Anisotropic magnetic coupling of permalloy micron dots forming a square lattice

Abstract

Static magnetic and spin wave properties of square lattices of permalloy micron dots with thicknesses of 500 and 1000 Å and with varying dot separations have been investigated. A magnetic fourfold anisotropy was found for the lattice with dot diameters of 1 μm and a dot separation of 0.1 μm. The anisotropy is attributed to an anisotropic dipole–dipole interaction between magnetically unsaturated parts of the dots. The anisotropy strength (order of ${10}^5\hspace{0.17em}{\mathrm{erg/cm}}^{\mathrm{3}}$ ) decreases with increasing in-plane applied magnetic field.